Search results for: mechanics
-
Perspective of High Energy Heating Implementation for Steel Surface Saturation with Carbon
Publication -
A new insight into understanding the Crow and Champagne preferred mode: a numerical study
Publication -
Simulation of Structure Formation Processes of Dissimilar Steels Welded Joints Using an Intermediate Layer
Publication -
Nutrient transport and acquisition by diatom chains in a moving fluid
PublicationThe role of fluid motion in delivery of nutrients to phytoplankton cells is a fundamental question in biological and chemical oceanography. In the study of mass transfer to phytoplankton, diatoms are of particular interest. They are non-motile, are often the most abundant components in aggregates and often form chains, so they are the ones expected to benefit most from enhancement of nutrient flux due to dissipating turbulence....
-
Management of low-temperature heat source by ORC aided by additional heat source
PublicationIn the paper presented is a concept to utilize waste heat from the power plant with the aid of the low-temperature ORC cycle. The ORC system is heated from two heat sources, the first one being the flow rate of waste heat obtained from the exhaust gases. Subsequently, the working fluid in the cycle is additionally heated by the condensing steam from the low pressure turbine extraction points increasing in such way the level of...
-
The Influence of Stretch Rod Speed on the Relationship between Preblown Bottle Aesthetic Quality and Final Blown Bottle Thickness Profile in Stretch Blow Molding from Preform Process
PublicationFrom a mechanical point of view, the aesthetic quality of preblown PET bottles and thickness profile of final blown PET bottles manufactured in ISBM process are determined by mechanical and thermal response of blown preforms. From the microscopic point of view the biggest influence on the mechanical and thermal properties of PET bottles have orientation and crystallization processes. From a technological point of view, the aesthetic...
-
Turbulence model evaluation for numerical modelling of turbulent flow and heat transfer of nanofluids
PublicationIn this work, Nusselt number and friction factor are calculated numerically for turbulent pipe flow (Reynolds number between 6000 and 12000) with constant heat flux boundary condition using nanofluids. The nanofluid is modelled with the single-phase approach and the simulation results are compared with experimental data. Ethylene glycol and water, 60:40 EG/W mass ratio, as base fluid and SiO2 nanoparticles are used as nanofluid...
-
Numerical modeling of the combustion in a lab-scale pulverized-coal fired combustion chamber
PublicationThis work presents results of numerical modeling of the combustion process inside a lab-scale drop-tube chamber, designed to investigate the slagging properties of the flue ashes, created through the solid fuel firing. Interaction between turbulence and chemistry is accounted by use of probability density function (PDF). FLUENT inputs for non-premixed combustion chemistry modeling are defined. A discrete second phase of the coal...
-
Influence of nanoparticle concentration on convective heat transfer of water-Al2O3 nanofluids inside horizontal tubes
PublicationNanofluids came to be seen as a new generation of coolants, especially in single-phase systems. Conducted experiments indicate that the increase in thermal conductivity is not the only reason for the intensification of heat transfer when using nanofluids. Preliminary results of the experimental investigation of the forced convection heat transfer of water-Al2O3 nanofluids inside stainless steel tube with 8 mm internal diameter...
-
Influence of nanoparticle concentration on thermal properties of thermal oil-MWCNT nanofluid
PublicationResults of the measurements of dynamic viscosity, thermal conductivity, electrical conductivity and pH of thermal oil-MWCNT (TO-MWCNT) nanofluid have been presented. Nanoparticles were tested at the concentration of 0.001%, 0.005%, 0.01%, 0.05%, and 0,1% by weight. Thermal oil (TO) was selected as a base liquid, because of possible application in ORC systems as an intermediate heating agent. Multi-walled carbon nanotubes were used...
-
Performance of a plate heat exchanger operated with water-Al2O3 nanofluid
PublicationThis study is focused on experimental investigation of a selected type of brazed plate heat exchanger (PHEx). The main aim of the paper was to experimentally check the ability of nanofluids to enhance the performance of PHEx. A typical water-Al2O3 nanofluid was tested and compared to that of the base fluid, i.e. water. Nanoparticles were tested at the concentration of 0.1% and 1% by weight. Impact of the 1 day and 3 days break...
-
Performance of the flat plate solar collector operated with water-Al2O3 nanofluid
PublicationThe paper discusses the effect of application of water-Al2O3 nanofluid, as a working fluid, on the efficiency of a flat plate solar collector. The mass concentration of nanoparticles was 0.1%, 0.2% and 0.4%. The tests were conducted for two values of radiation of about 1050 W/m2 and 400 W/m2, and volume flow rates of 60 l/h, 120 l/h and 170 l/h. The efficiency was calculated according to recommendations of the Polish Standard....
-
Beam on elastic foundation with anticlastic curvature: Application to analysis of mode I fracture tests
PublicationA first order correction is proposed taking into account both interface elasticity and transverse anticlastic curvature of flexible substrate(s) in the DCB (and related tests). Adherends are represented by Kirchhoff-Love plates, and the interface by Winkler-type elastic foundation. Two functions are introduced, representing evolution of beam deflection along the sample midline and anticlastic curvature along the plate. A method...
-
Experimental Validation of Numerical Model within a Flow Configuration of the Model Kaplan Turbine
PublicationThis paper investigates validation of flow within a model Kaplan turbine. This includes comparison of various turbulence models and their influence on torque and power generated by the turbine. Numerical results were compared with experimental data.
-
Behaviour of Colliding Multi-Storey Buildings under Earthquake Excitation Considering Soil-Structure Interaction
PublicationThis paper investigates the coupled effect of the supporting soil flexibility and pounding between neighbouring, insufficiently separated buildings under earthquake excitation. Two adjacent three-storey structures, modelled as inelastic lumped mass systems with different structural characteristics, have been considered in the study. The models have been excited using the time history of the Kobe earthquake of 1995. A nonlinear...
-
Multistage Coupling of Eight Mistuned Bladed Discs on Solid Shaft with 1% Mistuning
Publication -
Effect of a characteristic length on crack spacing in a reinforced concrete bar under tension
Publication -
Modelling and FE-simulation of plastic ductile damage evolution in plates and shells
Publication -
Elastic distortional buckling of thin-walled bars of closed quadratic cross-section
PublicationIn this study a tin-walled bar with closed quadratic cross-section is considered. The elastic stability of axially compressed bar related to the cross-section distortion is investigated. The governing differential equatio is derived with aid of the principle of stationary potential energy. The critical load for simply supported bar is found in an analytical form and it is copared with the FEM solution. Sufficient accuracy of the...
-
Strong ellipticity conditions and infinitesimal stability within nonlinear strain gradient elasticity
PublicationWe discuss connections between the strong ellipticity condition and the infinitesimal instability within the nonlinear strain gradient elasticity. The strong ellipticity (SE) condition describes the property of equations of statics whereas the infinitesimal stability is introduced as the positive definiteness of the second variation of an energy functional. Here we establish few implications which simplify the further analysis...
-
A chemo-mechano-thermodynamical contact theory for adhesion, friction, and (de)bonding reactions
PublicationThis work presents a self-contained continuum formulation for coupled chemical, mechanical, and thermal contact interactions. The formulation is very general and, hence, admits arbitrary geometry, deformation, and material behavior. All model equations are derived rigorously from the balance laws of mass, momentum, energy, and entropy in the framework of irreversible thermodynamics, thus exposing all the coupling present in the...
-
Bending analysis of functionally graded nanoplates based on a higher-order shear deformation theory using dynamic relaxation method
PublicationIn this paper, bending analysis of rectangular functionally graded (FG) nanoplates under a uniform transverse load has been considered based on the modified couple stress theory. Using Hamilton’s principle, governing equations are derived based on a higher-order shear deformation theory (HSDT). The set of coupled equations are solved using the dynamic relaxation (DR) method combined with finite difference (FD) discretization technique...
-
On thermal stability of piezo-flexomagnetic microbeams considering different temperature distributions
PublicationBy relying on the Euler–Bernoulli beam model and energy variational formula, we indicate critical temperature causes in the buckling of piezo-flexomagnetic microscale beams. The corresponding size-dependent approach is underlying as a second strain gradient theory. Small deformations of elastic solids are assessed, and the mathematical discussion is linear. Regardless of the pyromagnetic effects, the thermal loading of the thermal...
-
Computational analysis of an infinite magneto-thermoelastic solid periodically dispersed with varying heat flow based on non-local Moore–Gibson–Thompson approach
PublicationIn this investigation, a computational analysis is conducted to study a magneto-thermoelastic problem for an isotropic perfectly conducting half-space medium. The medium is subjected to a periodic heat flow in the presence of a continuous longitude magnetic field. Based on Moore–Gibson–Thompson equation, a new generalized model has been investigated to address the considered problem. The introduced model can be formulated by combining...
-
On nonlinear dilatational strain gradient elasticity
PublicationWe call nonlinear dilatational strain gradient elasticity the theory in which the specific class of dilatational second gradient continua is considered: those whose deformation energy depends, in an objective way, on the gradient of placement and on the gradient of the determinant of the gradient of placement. It is an interesting particular case of complete Toupin–Mindlin nonlinear strain gradient elasticity: indeed, in it, the...
-
On weak solutions of the boundary value problem within linear dilatational strain gradient elasticity for polyhedral Lipschitz domains
PublicationWe provide the proof of an existence and uniqueness theorem for weak solutions of the equilibrium problem in linear dilatational strain gradient elasticity for bodies occupying, in the reference configuration, Lipschitz domains with edges. The considered elastic model belongs to the class of so-called incomplete strain gradient continua whose potential energy density depends quadratically on linear strains and on the gradient of...
-
Local material symmetry group for first- and second-order strain gradient fluids
PublicationUsing an unified approach based on the local material symmetry group introduced for general first- and second-order strain gradient elastic media, we analyze the constitutive equations of strain gradient fluids. For the strain gradient medium there exists a strain energy density dependent on first- and higher-order gradients of placement vector, whereas for fluids a strain energy depends on a current mass density and its gradients....
-
Flexomagneticity in buckled shear deformable hard-magnetic soft structures
PublicationThis research work performs the first time exploring and addressing the flexomagnetic property in a shear deformable piezomagnetic structure. The strain gradient reveals flexomagneticity in a magnetization phenomenon of structures regardless of their atomic lattice is symmetrical or asymmetrical. It is assumed that a synchronous converse magnetization couples both piezomagnetic and flexomagnetic features into the material structure....
-
Thermal buckling of functionally graded piezomagnetic micro- and nanobeams presenting the flexomagnetic effect
PublicationGalerkin weighted residual method (GWRM) is applied and implemented to address the axial stability and bifurcation point of a functionally graded piezomagnetic structure containing flexomagneticity in a thermal environment. The continuum specimen involves an exponential mass distributed in a heterogeneous media with a constant square cross section. The physical neutral plane is investigated to postulate functionally graded material...
-
Numerical modelling of the mesofracture process of sintered 316L steel under tension using microtomography
PublicationThis paper concerns numerical modelling of the deformation process, taking into account the local fracture of porous 316L sinters at the mesoscopic scale using the finite element method. Calculations are performed with the use of geometrical models, to map the realistic shape of the porous mesostructure of the material, obtained by means of computed microtomography. The microtomographic device has limited and insufficient measurement...
-
Sensitivity analysis of free torsional vibration frequencies of thin-walled laminated beams under axial load
PublicationThe paper addresses sensitivity analysis of free torsional vibration frequencies of thin-walled beams of bisymmetric open cross-section made of unidirectional fibre-reinforced laminate. The warping effect and the axial end load are taken into account. The consideration is based upon the classical theory of thin-walled beams of non-deformable cross-section. The first-order sensitivity variation of the frequencies is derived with...
-
On existence and uniqueness of weak solutions for linear pantographic beam lattices models
PublicationIn this paper, we discuss well-posedness of the boundary-value problems arising in some “gradientincomplete” strain-gradient elasticity models, which appear in the study of homogenized models for a large class ofmetamaterials whosemicrostructures can be regarded as beam lattices constrained with internal pivots. We use the attribute “gradient-incomplete” strain-gradient elasticity for a model in which the considered strain energy...
-
Surface effects of network materials based on strain gradient homogenized media
PublicationThe asymptotic homogenization of periodic network materials modeled as beam networks is pursued in this contribution, accounting for surface effects arising from the presence of a thin coating on the surface of the structural beam elements of the network. Cauchy and second gradient effective continua are considered and enhanced by the consideration of surface effects. The asymptotic homogenization technique is here extended to...
-
Enriched buckling for beam-lattice metamaterials
PublicationWe discuss two examples of beam-lattice metamaterials which show attractive mechanical properties concerning their enriched buckling. The first one considers pantographic beams and the nonlinear solution is traced out numerically on the base of a Hencky’s model and an algorithm based on Riks’ arc-length scheme. The second one concerns a beam-lattice with sliders and the nonlinear solution is discussed in analytic way and, finally,...
-
Adaptation of the arbitrary Lagrange–Euler approach to fluid–solid interaction on an example of high velocity flow over thin platelet
PublicationThe aim of this study is to analyse the behaviour of a thin plate with air flow velocities of 0.3–0.9 Ma. Data from the experiment and numerical tools were used for the analysis. For fluid–solid interaction calculations, the arbitrary Lagrange–Euler approach was used. The results of the measurements are twofold. The first one is the measurement of the flow before and after vibrating plate, i.e. pure flow plate, and the second consists...
-
On the effective properties of foams in the framework of the couple stress theory
PublicationIn the framework of the couple stress theory, we discuss the effective elastic properties of a metal open-cell foam. In this theory, we have the couple stress tensor, but the microrotations are fully described by displacements. To this end, we performed calculations for a representative volume element which give the matrices of elastic moduli relating stress and stress tensors with strain and microcurvature tensors.
-
Improved model of isothermal and incompressible fluid flow in pipelines versus the Darcy–Weisbach equation and the issue of friction factor
PublicationIn this article, we consider the modelling of stationary incompressible and isothermal one-dimensional fluid flow through a long pipeline. The approximation of the average pressure in the developed model by the arithmetic mean of inlet and outlet pressures leads to the known empirical Darcy–Weisbach equation. Most importantly, we also present another improved approach that is more accurate because the average pressure is estimated...
-
Wideband Radio Direction Finder Implemented in Software Defined Radio Technology
PublicationIn the paper a wideband radio direction finder (RDF) implemented in software defined radio (SDR) technology and the results of hardware layer research, including developed antenna switching unit (ASU), are presented. The results of tests of the devices, which are the part of the software defined radio platform (SDRP), and antenna switching unit, confirmed the possibility of using selected components in the final solution.
-
Research and Analysis of Accuracy of Location Estimation in Inertial Navigation System
PublicationIn the article the research and analysis of digital signal processing and its influence on accuracy of location estimation in developed inertial navigation system was presented. The purpose of the system is to localize moving people in indoor environment. During research a measuring unit for recording selected movement parameters was made. In the article were also described author’s inertial navigation algorithms.
-
Size effect at aggregate level in microCT scans and DEM simulation – Splitting tensile test of concrete
PublicationThe paper describes an experimental and numerical study of size effect on concrete cylindrical specimens in splitting tensile test. Own experimental campaign was performed on specimens with 5 various diameters from D = 74, 105, 150, 192 and 250 mm with hardboard loading strips (distributed load according to standard methods) scaled proportionally to the specimen diameter. The crack opening-control system was applied to obtain the...
-
Nonlinear free and forced vibrations of a dielectric elastomer-based microcantilever for atomic force microscopy
PublicationThe majority of atomic force microcode (AFM) probes work based on piezoelectric actuation. However, some undesirable phenomena such as creep and hysteresis may appear in the piezoelectric actuators that limit their applications. This paper proposes a novel AFM probe based on dielectric elastomer actuators (DEAs). The DE is modeled via the use of a hyperelastic Cosserat model. Size effects and geometric nonlinearity are included...
-
Nonlinear strain gradient and micromorphic one-dimensional elastic continua: Comparison through strong ellipticity conditions
PublicationWe discuss the strong ellipticity (SE) conditions for strain gradient and micromorphic continua considering them as an enhancement of a simple nonlinearly elastic material called in the following primary material. Recently both models are widely used for description of material behavior of beam-lattice metamaterials which may possess various types of material instabilities. We analyze how a possible loss of SE results in the behavior...
-
Continuum models for pantographic blocks with second gradient energies which are incomplete
PublicationWe postulate a deformation energy for describing the mechanical behavior of so called pantographic blocks, that is bodies constituted by stacking of layers of pantographic sheets. We remark that the pantographic effect is limited in the plane of pantographic sheets and therefore only the second derivatives of transverse displacements along the pantographic fibers appear in the chosen deformation energy. We use this novel energy...
-
Fluid–solid interaction on a thin platelet with high-velocity flow: vibration modelling and experiment
PublicationThe paper concerns the nonlinear behaviour of a thin platelet that is streamlined in an aerodynamic tunnel. The air velocity in the aerodynamic tunnel was at 858.9 km/h or 0.7 Ma (Ma—Mach number is a dimensionless quantity in fluid dynamics representing the ratio of flow velocity past a boundary to the local speed of sound). This experiment was numerically simulated using FSI (fluid–solid interaction) tools, namely the coupling...
-
Strong ellipticity within the Toupin–Mindlin first strain gradient elasticity theory
PublicationWe discuss the strong ellipticity (SE) condition within the Toupin–Mindlin first strain gradient elasticity theory. SE condition is closely related to certain material instabilities and describes mathematical properties of corresponding boundary-value problems. For isotropic solids, SE condition transforms into two inequalities in terms of five gradient-elastic moduli.
-
Cavity-expansion approximation for projectile impact and penetration into sand
PublicationA one-dimensional problem of a spherical cavity expanding at a constant velocity from zero initial radius in an infinite granular medium, which has the first-kind self-similar solution, is considered. We are solving this dynamic spherical cavity-expansion problem to model rigid spheres penetrating into a granular media. Elastic–plastic deformation of the granular media is described in a barotropic approximation, using the high-pressure...
-
On solvability of initial boundary-value problems of micropolar elastic shells with rigid inclusions
PublicationThe problem of dynamics of a linear micropolar shell with a finite set of rigid inclusions is considered. The equations of motion consist of the system of partial differential equations (PDEs) describing small deformations of an elastic shell and ordinary differential equations (ODEs) describing the motions of inclusions. Few types of the contact of the shell with inclusions are considered. The weak setup of the problem is formulated...
-
A model of damaged media used for describing the process of non-stationary creep and long-term strength of polycrystalline structural alloys
PublicationThe main laws of the processes of creep and long-term strength of polycrystalline structural alloys are considered. From the viewpoint of continuum damaged media (CDM), a mathematical model is developed that describes the processes of viscoplastic deformation and damage accumulation under creep. The problem of determining material parameters and scalar functions of the developed constitutive relations based on the results of specially...
-
Laplace domain BEM for anisotropic transient elastodynamics
PublicationIn this paper, we describe Laplace domain boundary element method (BEM) for transient dynamic problems of three-dimensional finite homogeneous anisotropic linearly elastic solids. The employed boundary integral equations for displacements are regularized using the static traction fundamental solution. Modified integral expressions for the dynamic parts of anisotropic fundamental solutions and their first derivatives are obtained....
-
On dynamic modeling of piezomagnetic/flexomagnetic microstructures based on Lord–Shulman thermoelastic model
PublicationWe study a time-dependent thermoelastic coupling within free vibrations of piezomagnetic (PM) microbeams considering the flexomagnetic (FM) phenomenon. The flexomagneticity relates to a magnetic field with a gradient of strains. Here, we use the generalized thermoelasticity theory of Lord–Shulman to analyze the interaction between elastic deformation and thermal conductivity. The uniform magnetic field is permeated in line with...